#100以内的奇数和
#P37048 （2021-4-1）

sum_hundred = 0
hundred = 100

#头脑中第一个想到的做法
# while hundred:
#     if hundred % 2 != 0:
#         sum_hundred += hundred
#     hundred -= 1
#     print(hundred,sum_hundred)
# print(sum_hundred)

#注意continue前要自减，否则就会死循环
# while hundred:
#     if hundred % 2 == 0:
#         hundred -= 1
#         continue
#     else:
#         sum_hundred += hundred
#         #print(hundred,sum_hundred)
#     hundred -= 1
# print(sum_hundred)

#for循环
# for i in range(1,100,2):
#     sum_hundred += i
# print(sum_hundred)

#位与，据说位与运行算法最快
while hundred:
    if hundred & 1 == 1:
        sum_hundred += hundred
    hundred -= 1
print(sum_hundred)